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    <title>Document</title>
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<script>
    // string number boolean null undefined  => 值类型 (普通数据类型)
    // array  object                         => 引用类型(特殊数据类型  对象都是引用类型)

    var a = 1;
    var b = a;  // b = 1;
    var b = 2;  // b = 2;
    console.log(a,b); // 1  2

    var arr = [1,2,3];
    var brr = arr;  // brr = [1,2,3]
    brr.push(4);    // brr = [1,2,3,4]
    console.log(arr,brr,arr === brr);

    // arr和brr共有同一片内存空间只要有一个改变  另一个也会改变  => 浅复制(===)




</script>
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